A blender is one of electrical appliances which are most frequently used in the home today. The blender chops foods such as fruits, vegetables and cereal into small pieces which can be ingested.
Once a food to be chopped is put in a storage container of the blender and the container is closed with a lid, the motor is driven at a high speed to rotate blades. In this process, a lot of bubbles are formed as grains of the chopped food are mixed with air in the storage container. When fruits such as bananas or tomatoes are put in the blender and chopped, a large amount of bubbles is generated over the fruit juice. The generated bubbles not only means that taste and texture of the fruit juice is lowered when the fruit juice is ingested and that a considerable portion of nutrients in the fruit has been destroyed as fibers in the fruit are oxidized in the chopping process.
In addition, if the chopped food is kept exposed in the air rather than being ingested immediately after being chopped, oxidization of the food further proceeds, which accelerates disruption of the fiber and nutrients, discolors the food along with degradation of freshness of the food, and results in separation of the food and air into layers. Thus, once a food is chopped by the blender, it is difficult to keep the chopped food for a long time without ingesting the food.
A vacuum blender capable of chopping foods in a vacuum space has been developed to solve the aforementioned problem. An example of the vacuum blender is disclosed in Japanese Patent Application Publication No. 2013-111079 (High-speed vacuum stirring method for bubble-free fruit juice/food, and mixer for the same) (Reference 1). According to the vacuum mixer of this document, a mixer drum is covered by a seal lid, a vacuum throat provided to the seal lid is connected with a selector valve, an intake valve, a vacuum pump and a pressure gauge via a vacuum tube.
According to a method for operating the vacuum mixer, a food is put in the mixer drum and then the seal lid is put on the drum. Then, the air is discharged from the drum through the vacuum throat connected to the seal lid. Then, the selector valve is operated to connect the seal lid and the vacuum pump. When a vacuum pressure less than or equal to 300 mbar is obtained, the motor of the mixer operates to stir the food. Once the stirring operation is completed, the vacuum pump is stopped and the intake valve opens to release the vacuum condition and allow the seal lid to be easily separated.
However, such vacuum mixer needs to employ a vacuum device configured by connecting various components such as a vacuum pump, a selector valve, an intake valve and a pressure gauge on the outside of a typical mixer in a complex manner. Accordingly, it is very inconvenient to operate the mixer. Moreover, after the mixer is used, the vacuum device needs to be separated from the mixer and stored separately, which causes inconvenience.
Moreover, with such vacuum mixer, the intake valve begins to open to introduce air into the mixer drum as soon as the operation of the vacuum pump is stopped. Accordingly, the chopped food cannot be left in the drum in a vacuum state for a long time.